The present invention relates to an image forming apparatus and, more particularly, to a paper feeder to feeding papers to an image forming apparatus and a paper tray elevation device therefore.
Generally, a copier, printer, facsimile apparatus or similar image forming apparatus extensively used today has a paper feeder therein for feeding papers to be recorded with images. Particularly, an electrophotographic copier expected to deal with a relatively small number of papers at a time usually has a paper feeder facilitating the replenishment of papers, easy to operate, and capable of feeding even a great number of papers, as needed. For example, Japanese Patent Laid-Open Publication Nos. 5-124737, 5-221536, 6-144600 and 7-137851 each discloses a so-called front loading paper feeder allowing the operator to replenish papers at the front of an apparatus on which the paper feeder is mounted, and capable of automatically replenishing papers without interrupting paper feed under way.
The paper feeder includes a paper tray elevation device for causing a paper tray loaded with a stack of papers to move up and down. For the elevation device to move the paper tray up and down, use has customarily been made of either one of a cantilever system and a horizontal elevation system or wire system. However, the problem with the conventional elevation device, whether it be of the cantilever system or the horizontal elevation system, is that when papers of relatively great size or a great number of papers are stacked on the tray, the papers cannot be held in an adequate or stable position on the tray. Specifically, such papers are irregularly positioned, deformed or fed in an unstable condition.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 59-211061, 5-229243, 5-306025, 6-40137, and 6-72566.